This invention relates generally to ink jet printers and more particularly to monitoring the quantity of ink in the ink cartridges of an ink jet printer.
The typical ink jet printer employs a print head assembly, comprising one or more ink cartridges, mounted on a carriage assembly. Each ink cartridge comprises an ink reservoir and a printhead formed with very small nozzles through which ink drops are dispensed. The print head assembly is moved laterally back and forth over the width of a sheet of paper or other print media by the carriage assembly to dispense the ink drops from the nozzles onto the print media in patterns determined by electrical control signals from a printer controller.
Ink jet printers typically have a cleaning station usually located at one extreme of the carriage travel for cleaning of the printhead nozzles. The carriage assembly periodically returns to the cleaning station after a predetermined amount of ink has been dispensed from the ink cartridges.
There are, typically, four ink cartridges in color ink jet printers, the individual ink cartridges holding cyan, magenta, yellow and black ink. Each color is likely to be dispensed at a different rate depending upon the type of images being printed. It is desirable for a user to know the quantity of the ink in each ink cartridge at any given time. This allows a user to refill or replace a cartridge prior to the cartridge becoming completely empty, avoiding a defective print job or damage to a printhead.
It is also useful to log the ink consumption of each ink cartridge over time and/or in relation to each print job in order to compute the ink consumption and cartridge replacement information, cost per page information etc. The ink consumption information is useful to both the user, for estimating purchasing/stock requirements and cost analysis etc., and to the manufacturer of the ink cartridge to improve its marketing/distribution/customer support operations.
A variety of approaches have been proposed for measuring the quantity of ink in ink jet cartridges installed in ink jet printers. U.S. Pat. No. 5,079,570 describes an ink level sensor employing a light beam for detecting the level of ink in a cartridge employing a capillary ink reservoir. However, the sensor is capable of detecting only whether or not the ink is above or below a certain level in the cartridge. U.S. Pat. Nos. 5,610,635 and 5,691,750 each disclose a technique for estimating the amount of ink remaining in an ink jet printer ink cartridge based upon the fluid volume of a dispensed ink drop and the number of times the printhead is energized to dispense the ink. U.S. Pat. Nos. 5,788,388 and 5,712,667 each disclose an ink level sensor in which a light emitting diode and a light detector are arranged across a sump at the bottom of an ink cartridge to detect when the ink in the sump falls below a selected level. U.S. Pat. No. 5,744,136 discloses a means for directly measuring the ink level in an ink cartridge by measuring the transit time of an ultrasonic pulse transmitted through the ink in the ink cartridge. All of the aforementioned approaches suffer from either an inability to directly measure the actual level of ink in an installed ink cartridge or from excessive complexity.
Accordingly there is a need for an accurate, economical and reliable means for automatically measuring and recording the quantity of the ink in an ink jet printer ink cartridge while the ink cartridge is installed in an ink jet printer. There is further a need for a user to be able to determine the ink level by visual inspection of the cartridge. In addition, there is a need to automatically read and store information placed on the cartridge by the manufacturer to identify specific information about each cartridge. None of the above prior art methods provide all of these features.
The present invention is directed to a ink detection apparatus for periodically and automatically measuring the quantity of ink stored in an ink jet printer cartridge while the ink cartridge is installed in a printing mechanism. The invention further provides a means for automatically reading manufacturer information codes from each ink cartridge, means for storing the ink level information and manufacturer information codes in the printer memory or in a connected computer memory and means for logging cartridge ink consumption and generating ink consumption statistics for use by users and manufacturers.
Briefly stated the present invention is an apparatus for recording information about an ink cartridge installed in a printing mechanism comprising: an indicator internal to the ink cartridge for providing the information about the ink cartridge; a sensor, external to the ink cartridge, for receiving the information from the indicator; and a controller for receiving the information from the sensor and storing the information.
The present invention further comprises an apparatus for determining information about an ink cartridge installed in a printing mechanism comprising: a carriage assembly reciprocating on a carriage guide rod, the ink cartridge being mounted on the carriage assembly for movement therewith, the ink cartridge including a rear wall and an ink reservoir for holding a quantity of ink; a movable indicator located within the ink cartridge, the indicator having a surface adjacent to the rear wall of the ink cartridge, the indicator, by its location in the ink cartridge, providing information about the ink cartridge; and a sensor for receiving the information from the indicator about the ink cartridge.
The present invention further comprises an ink cartridge for a printing mechanism comprising: a reservoir holding ink and a movable indicator internal to the ink cartridge, a location of the indicator corresponding to the quantity of ink in the reservoir.